Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nucleoside antagonists of human immunodeficiency virus (HIV) reverse transcriptase (RT) activity have been commonly used in the therapy of HIV-associated disease. The prolonged use of such drugs has led to the development of HIV variants that display resistance against these compounds. HIV drug resistance has been documented clinically for each of the following nucleosides: 3'-azido-3'-deoxythymidine (AZT; zidovudine, ZDV), 2',3'-dideoxyinosine (ddI; didanosine), and 2',3'-dideoxycytidine (ddC; zalcitabine). In addition, resistance has been demonstrated against a series of non-nucleoside inhibitors of the viral RT. Several groups have documented that a series of point mutations within the HIV pol gene, that encodes the RT enzyme, is responsible for HIV drug resistance. Diminished sensitivity to anti-viral drugs results from both the selective pressure exerted by these compounds in individuals receiving prolonged therapy and the error-prone nature of the viral RT itself, thus permitting the outgrowth of mutated forms. Patients suffering from both disease progression and/or low CD4 counts are most likely to develop HIV drug resistance.
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PMID:Development and significance of nucleoside drug resistance in infection caused by the human immunodeficiency virus type 1. 752 16

Some aza and deaza analogues of the anti-HIV agent 2',3'-dideoxy-3'-oxoadenosine (isoddA) (8-aza-, 8-aza-1-deaza, 8-aza-3-deaza-, 1-deaza-, and 3-deaza-isoddA) were synthesized and found inactive against HIV in vitro. The hypothesis that the inactivity of these isonucleosides might be due to their poor affinity for cellular nucleoside kinases was checked by the synthesis of a series of 5'-[bis(2,2,2-trichloroethyl) phosphate] triesters and 5'-phenyl phosphoramidate derivatives which, acting as membrane soluble prodrugs, could release the free phosphate form inside the cell. The 5'-(phenylmethoxy)alaninyl phosphate derived from 8-aza-isoddA was found active against HIV-1 and HIV-2 with a potency similar to that of isoddA, while the anti-HIV potency of 5'-(phenylmethoxy)alaninyl phosphate of isoddA proved remarkably higher than that of isoddA, in particular against HIV-2, being similar to that of AZT. Further evidence that 8-aza-isoddA could behave as anti-HIV agent, provided that it is activated as phosphate, was obtained by the synthesis of its 5'-triphosphate derivative, which proved to be an active inhibitor of HIV-1 recombinant reverse transcriptase.
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PMID:Synthesis and evaluation of the anti-HIV activity of aza and deaza analogues of isoddA and their phosphates as prodrugs. 752 75

Appropriately protected nucleoside 5'-O-(2-thio-1,3,2-dithiaphospholanes) react with inorganic pyrophosphate in the presence of a strong base catalyst (DBU) to give nucleoside 5'-O-(1,1-dithiotriphosphates) 1a-g. The latter compounds, including an AZT analogue, show modest antivirial activity against HIV-1 and HIV-2 replication in CEM cells. The AZT and deoxyadenosine derivatives were found to be inhibitors of HIV reverse transcriptase.
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PMID:The synthesis of nucleoside 5'-O-(1,1-dithiotriphosphates). 752 60

Forty-two dihydroseselins based on the structure of suksdorfin (1) were synthesized in order to evaluate their anti-HIV activity. These synthetic derivatives include 3',4'-di-O-acyl- and 3'- or 4'-O-acyl-cis-dihydroseselins (8-21) and 3',4'-trans-dihydroseselins with O-acyl and/or O-alkyl groups at the 3' and 4' positions (6, 22-43). Two 4'-azido (44, 45) and three 4'-alkylamido (46, 48, 49) derivatives were also prepared. By using optically pure reagents, three pairs of diastereoisomers were synthesized and separated as optically pure compounds (14, 15; 16, 17; 38, 39). Together with the above synthetic derivatives, seselin (3) and (+/-)-cis-(4), (+)-cis- (5), and (+/-)-trans-dihydroseselin-3',4'-diol (7) were also tested for their in vitro anti-HIV activity. An optically pure compound, 3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (16), showed potent inhibitory activity and remarkable selectivity against HIV replication. The EC50 value and in vitro therapeutic index (TI) of 16 are 4 x 10(-4) microM and 136,719, respectively, which are better than those shown by AZT in the same assay. In addition, compound 16 is also active against HIV replication in a monocytic cell line and in peripheral blood mononuclear cells (PBMCs). Our in vitro assay indicated that, like compound 1, compound 16 is not an inhibitor of HIV-1 reverse transcriptase. Moreover, the anti-HIV activity of 16 is stereoselective as its three diastereoisomers (17, 38, 39) are at least 10,000 times less active. Since other synthetic dihydroseselin derivatives with different substituents or without any substituents are inactive or are active only at much higher concentration, the antiviral potency of 16 could be associated with the camphanoyl moieties of its structure. Therefore, compound 16 represents a unique coumarin structure with promising anti-HIV activity.
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PMID:Anti-AIDS agents. 15. Synthesis and anti-HIV activity of dihydroseselins and related analogs. 752 62

5-Chloro-2',3'-dideoxy-3'-fluorouridine (935U83) is a selective anti-human immunodeficiency virus (HIV) agent. When tested in phytohemagglutinin-stimulated normal human peripheral blood lymphocytes against fresh clinical isolates of HIV type 1 (HIV-1) obtained from patients naive to AZT (3'-azido-3'-deoxythymidine [zidovudine]), 935U83 inhibited virus growth with an average 50% inhibitory concentration (IC50) of 1.8 microM; corresponding IC50s were 0.10 microM for FLT (3'-deoxy-3'-fluorothymidine) and 0.23, 0.49, and 0.03 microM for the approved agents AZT, ddI (2',3'-dideoxyinosine), and ddC (2',3'-dideoxycytosine), respectively. Importantly, 935U83 retained activity against HIV strains that were resistant to AZT, ddI, or ddC. Of additional interest, we were unable to generate virus which was resistant to 935U83 by passaging either HXB2 (AZT-sensitive) or RTMC (AZT-resistant) strains in the presence of high concentrations of 935U83. The anabolic profile of 935U83 was similar to that of AZT, and 935U83 triphosphate was a potent inhibitor of HIV-1 reverse transcriptase. Pharmacokinetic evaluation showed good oral bioavailability (86% in mice and 60% in monkeys) and less extensive metabolism to the glucuronide relative to AZT. 935U83 showed low toxicity. In an in vitro assay for toxicity to a human erythrocyte progenitor, erythroid burst-forming unit (BFU-E), the IC50 for 935U83 (> 400 microM) was more than 1,000-fold those of FLT (0.07 microM) and AZT (0.30 microM). Mild reversible reductions in erythrocytes and associated parameters were seen in mice dosed orally with 2,000 mg of 935U83 per kg per day for 1 and 6 months. In monkeys dosed orally with up to 700 mg/kg/day for 1 and 6 months, the only possible treatment-related finding was cataracts in 1 of 12 animals given the intermediate dose of 225 mg/kg/day. At the highest doses in mice and monkeys, maximal concentrations in plasma were more than 100-fold the anti-HIV IC50s against clinical isolates. This safety profile in animals compares very favorably with that of any of the anti-HIV drugs approved to date and has led us to begin evaluation of 935U83 in patients with HIV infection.
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PMID:5-Chloro-2',3'-dideoxy-3'-fluorouridine (935U83), a selective anti-human immunodeficiency virus agent with an improved metabolic and toxicological profile. 752 82

A series of benzothiadiazine derivatives were screened against the human immunodeficiency virus (HIV) and certain structure-activity relationships were defined for anti-HIV activity in this chemical class. The selected representative NSC 287474 was a highly potent inhibitor of HIV-induced cell killing and HIV replication in a variety of human cell lines, as well as in fresh human peripheral blood lymphocytes and macrophages. The compound was active against a panel of biologically diverse laboratory and clinical strains of HIV-1, including the AZT-resistant strain G910-6. However, the agent was inactive against HIV-2, and also against both nevirapine- and pyridinone-resistant strains (N119 and A17) of HIV-1, which are cross-resistant to several structurally diverse nonnucleoside reverse transcriptase inhibitors. The compound selectively inhibited HIV-1 reverse transcriptase, but not HIV-2 reverse transcriptase. Combination of NSC 287474 with AZT synergistically inhibited HIV-1-induced cell killing in vitro. The compound did not inhibit the replication of the Rauscher murine leukemia retrovirus or the simian immunodeficiency virus. The benzothiadiazine class of compounds represents a new active anti-HIV-1 chemotype within the diverse group of nonnucleoside reverse transcriptase inhibitors.
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PMID:Biological and biochemical anti-HIV activity of the benzothiadiazine class of nonnucleoside reverse transcriptase inhibitors. 752 14

DNA amplification systems are powerful technologies with the potential to impact a wide range of diagnostic applications. In this study we explored the feasibility and limitations of a modified ligase chain reaction (Gap-LCR) in detection and discrimination of DNAs that differ by a single base. LCR is a DNA amplification technology based on the ligation of two pairs of synthetic oligonucleotides which hybridize at adjacent positions to complementary strands of a target DNA. Multiple rounds of denaturation, annealing and ligation with a thermostable ligase result in the exponential amplification of the target DNA. A modification of LCR, Gap-LCR was developed to reduce the background generated by target-independent, blunt-end ligation. In Gap-LCR, DNA polymerase fills in a gap between annealed probes which are subsequently joined by DNA ligase. We have designed synthetic DNA targets with single base pair differences and analyzed them in a system where three common probes plus an allele-specific probe were used. A single base mismatch either at the ultimate 3' end or penultimate 3' end of the allele specific probe was sufficient for discrimination, though better discrimination was obtained with a mismatch at the penultimate 3' position. Comparison of Gap-LCR to allele-specific PCR (ASPCR) suggested that Gap-LCR has the advantage of having the additive effect of polymerase and ligase on specificity. As a model system, Gap-LCR was tested on a mutation in the reverse transcriptase gene of HIV, specifically, one of the mutations that confers AZT resistance. Mutant DNA could be detected and discriminated in the presence of up to 10,000-fold excess of wild-type DNA.
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PMID:Detection of point mutations with a modified ligase chain reaction (Gap-LCR). 753 8

Zidovudine (azidothymidine, AZT), a drug used in acquired immune deficiency syndrome (AIDS), blocks reverse transcriptase and therefore inhibits human immunodeficiency virus (HIV) replication. We carried out an ultrastructural and histoenzymatic study in rat cardiac muscle. Groups of animals (3 rats per group) were given drinking water with or without AZT (1 or 2 mg AZT/ml). After 30, 60 and 120 days, the hearts were studied by light and electron microscopy. Histochemical analysis of isocitrate, succinic, malic, NADH and NADPH dehydrogenase activities revealed no changes in AZT-treated rats compared with control rats. The ultrastructural study showed a disruption of cristae and an increased size of mitochondria in rats treated with AZT for 30- and 60-days. No alterations were observed in rats that received the 120-day treatment. A statistical analysis based on electron micrographs demonstrated a time-dependent ratio between intact and disrupted mitochondria. Rats that received AZT for 30 days showed a higher number of abnormal mitochondria than rats that received the 60 day treatment. No differences with respect to rat controls were observed in the rats that received AZT for 120 days. We conclude that AZT-induced ultrastructural alterations in cardiac muscle did not modify the histochemical activity of several mitochondrial enzymes.
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PMID:Histochemical and ultrastructural changes induced by zidovudine in mitochondria of rat cardiac muscle. 753 28

A lysine-to-arginine substitution at amino acid 65 (K65R) in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) is associated with resistance to 2',3'-dideoxycytidine (ddC), 2',3'-dideoxyinosine (ddI), and the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine (3TC). To further characterize the molecular basis of such resistance, we expressed the pp6/p51 heterodimer of wild-type RT, K65R mutated RT, and a doubly mutated (K65R/M184V) RT in Escherichia coli and assessed the characteristics of nucleotide incorporation and chain termination in cell-free reverse transcription reactions in the presence and absence of various nucleoside triphosphate analogs. These reactions employed a HIV RNA template (HIV-PBS) that contained the primer binding sequence (PBS) and the U5 and R regions of HIV-1 genomic RNA and an oligodeoxynucleotide (dPR) complementary to the HIV-1 PBS as primer. The K65R and K65R/M184V RTs showed significantly decreased chain-termination effects during polymerization with the 5'-triphosphates of ddC, 3TC, 2',3'-dideoxyadenosine, and AZT (3'-azido-3'-deoxythymidine) in comparison with wild-type RT. Detailed analysis with ddCTP and wild-type RT revealed that chain termination occurred at all guanines in the RNA template. However, the frequency of dideoxynucleoside triphosphate (ddNTP)-induced chain termination was decreased at certain guanines but not others in reactions catalyzed by K65R RT. Both the K65R mutant RT and wild-type RT had similar processive activity. These results indicate that decreased chain termination of K65R RT in the presence of ddNTPs is consistent with data obtained in viral replication assays.
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PMID:Mutated K65R recombinant reverse transcriptase of human immunodeficiency virus type 1 shows diminished chain termination in the presence of 2',3'-dideoxycytidine 5'-triphosphate and other drugs. 753 30

Human immunodeficiency virus type 1 (HIV-1) isolates obtained from the blood of patients undergoing treatment with 3'-azido-3'-deoxythymidine (zidovudine [AZT]) show a decreased sensitivity to the drug in vitro. The aim of the present study was to determine if HIV-1 variants resistant to AZT are present also in the brain compartment. We selected sequential HIV-1 isolates from the blood and the cerebrospinal fluid (CSF) of six patients with HIV-1 infection undergoing AZT therapy for a time varying between 1 and 3 years. The isolates were used to infect peripheral blood mononuclear cell cultures which were used to prepare viral DNA. The viral DNA was amplified by PCR and then directly sequenced. Analysis of the reverse transcriptase (RT) sequence of the isolates from the CSF during therapy demonstrated that CSF-resistant isolates are characterized by the same mutations documented in resistant isolates from the blood compartment. Isolates obtained from one patient (patient 3) showed the same two mutations (codons 70 and 215) in blood and CSF, whereas isolates obtained from an additional four patients presented a different pattern of mutations in the two compartments. We also analyzed the degree of amino acid homology between RT sequences from blood and CSF isolates in patients before and during AZT treatment. The percentages of amino acid variations were approximately equal when isolates from the same or different compartments were considered. Excluding the codons involved in AZT resistance, the time point of sampling did not affect RT variations during therapy significantly. In conclusion, our studies show that AZT-resistant HIV-1 can be found in the CSF of patients undergoing treatment. The mutations linked to AZT resistance in the CSF isolates are the same as those identified in AZT-resistant isolates from blood.
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PMID:Reverse transcriptase sequence of paired isolates of cerebrospinal fluid and blood from patients infected with human immunodeficiency virus type 1 during zidovudine treatment. 753 14


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